The present application claims priority to Japanese Application No. P10-256381 filed Sep. 10, 1998 which application is incorporated herein by reference to the extent permitted by law.
1. Field of the Invention
This invention relates to a display apparatus, and more particularly to a display apparatus which employs a display panel to display an image.
2. Description of the Prior Art
FIG. 1 shows a conventional display apparatus which employs a display panel for which a liquid crystal display panel is used. The display apparatus includes a chassis 1. The chassis 1 is formed by bending a sheet metal of an aluminum alloy. The chassis 1 is open on the front side and has a side face opening 2 formed on the right-hand side face such that a box-shaped lighting apparatus 3 in the form of a unit can be inserted into the chassis 1 through the side face opening 2. The opening on the front side of the chassis 1 allows light from the lighting apparatus 3 to go out forwardly therethrough. The lighting apparatus 3 is used as a backlight. Usually, a side edge backlight type apparatus or a direct backlight type apparatus is used for the lighting apparatus 3.
A panel holder 4 is combined on the front face side of the chassis 1. The panel holder 4 is formed from a frame member which supports a liquid crystal panel 6 thereon. The liquid crystal panel 6 is adhered to the panel holder 4 with a double-sided adhesive tape 5 and is attached to the front face of the chassis 1 together with the panel holder 4 by means of screws 7.
A circuit board 8 of the display apparatus is mounted on the rear face side of the chassis 1. The chassis 1 has a pair of short legs 9 provided on the opposite sides of a lower portion thereof and is supported on a support base 10 through the legs 9.
The lighting apparatus 3 in the form of a unit accommodated in the chassis 1 is described below with reference to FIG. 2. The lighting apparatus 3 shown in FIG. 2 is of the direct backlight type and includes a plurality of fluorescent lamps 13 disposed in a juxtaposed relationship with each other and serving as light sources. A reflecting plate 14 is disposed on the rear face side of the fluorescent lamps 13, and a circuit board 16 for energizing the fluorescent lamps 13 is disposed on the rear side of the reflecting plate 14. The circuit board 16 is mounted on a casing 15.
An optical panel 17 for eliminating non-uniformity of the luminance is mounted on the front face of the lighting apparatus 3.
The optical panel 17 includes a combination of three members of a rear face side diffusion plate 18, a prism sheet 20 and a diffusion plate 19.
The rear face side diffusion plate 18 is used to diffuse the light to reduce non-uniformity of the luminance. This is because the location in front of each of the fluorescent lamps 13 is liable to be brighter than any other location.
The prism sheet 20 is disposed on the rear face side diffusion plate 18. The prism sheet 20 is provided to condense the light of the fluorescent lamps 13 on the front to augment the luminance on the front.
The diffusion plate 19 is disposed on the prism sheet 20. The diffusion plate 19 prevents a moire which is caused by the combination of the prism sheet 20 and the liquid crystal panel 6.
The optical panel 17 is attached to the casing 15 by means of a pair of holding members 21.
When the lighting apparatus 3 is incorporated in the chassis 1 of the display apparatus having the structure described above with reference to FIG. 1, the chassis 1 surrounds the lighting apparatus 3. Consequently, the display apparatus has a dual box structure including the chassis 1 and an armor formed from the casing 15 of the lighting apparatus 3. Accordingly, application of the structure to a display apparatus of a large screen gives rise to a problem that the display apparatus becomes heavy in weight. Further, when the lighting apparatus 3 is taken out of the chassis 1, the strength of the chassis 1 against torsion becomes very low. Therefore, the display apparatus is disadvantageous in that, if an unnecessary force acts upon the chassis 1 while the lighting apparatus 3 is not accommodated in the chassis 1 such as, for example, upon assembly of the display apparatus, the chassis 1 is distorted or the lighting apparatus 3 becomes less liable to be inserted into the chassis 1.
Further, with the display apparatus shown in FIG. 1, when the lighting apparatus 3 is inserted into or removed from the chassis 1, the optical panel 17 shown in FIG. 2 is sometimes damaged or soiled. In order to prevent non-uniform luminance caused by such damage or soil from appearing conspicuously, it is necessary to attach a thin diffusion plate to the back face side of the liquid crystal panel 6. The panel holder 4 of FIG. 1 is provided to this end. If the panel holder 4 is omitted in order to reduce the weight of the set, then a thin diffusion plate for prevention of non-uniform luminance cannot be attached and therefore the liquid crystal panel 6 is attached directly to the chassis 1 by means of the double-sided adhesive tape 5. The structure just described, however, has a problem in that non-uniform brightness originating from damage or soil to the optical panel is not reduced and an undesirable stress is applied to the liquid crystal panel 6 by a distortion of the chassis 1.
Some of display apparatus which employ, for example, a small-size liquid crystal panel of 14 inches or less employ a lighting apparatus in the form of a unit as a chassis. More particularly, a liquid crystal display panel is attached directly to the front face of a lighting apparatus, and a circuit board is mounted on the rear face of the lighting apparatus. The structure is superior in that it allows realization of reduction in weight and miniaturization of a display apparatus. However, it is disadvantageous in that time is required for replacement of a light source of the lighting apparatus.
It is an object of the present invention to provide a display apparatus which has a large screen with a light weight and a sufficient structural strength and allows easy replacement of a light source of a lighting apparatus.
In order to attain the object described above, according to an aspect of the present invention, there is provided a display apparatus including a display panel for displaying an image thereon, including a rectangular frame formed from a combination of bar members corresponding to four sides of the display panel, and a circuit board for driving the display panel mounted on the frame together with the display panel.
With the display apparatus, since the frame serves also as a chassis and besides has a rectangular shape composed of a combination of bar members corresponding to the four sides of the rectangle, a sufficient strength is assured.
The display apparatus may be constructed such that each of the bar members which form the frame is a polygonal tube-like member, and the polygonal tube-like member of at least one of the bar members has a groove for holding a part or a unit of the display apparatus. Further, the display apparatus may be constructed such that the bar member is formed from a molded member, and the groove is formed in the molding direction. The frame may support a light source unit of the display panel and serves also as a casing for the light source unit. The light source unit may include a plurality of linear light sources mounted on a reflecting plate and is removably mounted on the frame. The display apparatus may be constructed such that an opening is formed in the bar member of one of the four sides of the frame and a guide groove is formed on each of a pair of the bar members on the opposite sides of the one side with the opening, and a part or a unit of the display apparatus is inserted into the frame through the opening and held by the guide grooves.
According to another aspect of the present invention, there is provided a display apparatus, comprising a rectangular frame, a display panel attached to the front face side of the frame, and a light source unit including a light source, a reflecting plate and an optical panel, the light source unit being accommodated in and held by the frame.
With the display apparatus, the display panel, light source unit and optical panel can be mounted on the rectangular frame to assembly the display apparatus. Consequently, the display apparatus is simple in structure and is composed of a comparatively small number of parts.
The light source unit may be inserted into the frame through an opening of the frame and held by grooves on the inner side of the frame. Alternatively, the light source unit may be inserted into the frame through an opening on the rear face side of the frame.
In a preferred form of the present invention, a panel type display apparatus includes a frame which is composed of a rectangular framework composed of a combination of four bar members and serves also as a chassis to which a display panel, a circuit board and other components are attached. For the members of the chassis of the frame structure type, extruded or drawn members are used. The members may be groove steel bars or polygonal steel pipes on which grooves extending in the extruding or drawing direction can be formed readily and which is light in weight and high in bending strength, and grooves for holding a light source unit or an optical panel are preferably formed on the members upon molding.
By attaching a light source to the rear face of the chassis of the frame structure and attaching the optical panel to the front face of the chassis, the chassis of the frame structure can be used as a casing for the lighting apparatus, and optical parts such as the light source, a reflecting plate and a diffusion plate, a circuit board and so forth can be attached in units of a part or as a unit to the chassis of the frame structure. In particular, when compared with a conventional structure of a display apparatus wherein a lighting apparatus covered with a box-shaped casing is mounted on a chassis, in the lighting apparatus of the present invention, the chassis serves also as a casing for the lighting apparatus. Accordingly, the weight of the display apparatus can be reduced. Preferably, in order to facilitate assemblage of the display apparatus, a fluorescent lamp serving as the light source is attached to the reflecting plate to form an integrated light source unit.
Further, where an opening is provided on one of a side face, an upper face and a lower face of the chassis of the frame structure, the light source unit wherein the light source is attached to the reflecting plate and the optical panel are inserted into and removed from the chassis through the opening and also they are slidably moved along guide grooves provided on the chassis of the frame structure, replacement of the light source can be performed with more simply.
A significant characteristic of the display apparatus having the construction described above resides in that reduction in weight of the set can be achieved particularly where a display panel of a large size is employed and reduction in cost of the set chassis and the lighting apparatus can be achieved and besides simplicity in replacement of the light source is achieved.
A large-screen plasma display unit or a like unit is in a situation far from being called wall-mounted display unit in terms of the luminance, weight and so forth. In particular, a plasma display unit of the 42-inch size has a weight of 50 to 70 kg. In contrast, a display apparatus to which the present invention is applied can be produced with a set weight of 30 to 40 kg.
This is described more specifically. A display apparatus which employs a conventional display panel in almost all cases employs a liquid crystal panel of an approximately 14-inch size and is small in size. However, a plasma-addressed liquid crystal panel has been developed in recent years, and a large-size liquid crystal display apparatus of a 40-inch size or more are being developed. The present invention is directed to a structure suitable for a display apparatus which includes a large-size lighting apparatus and is fundamentally different in concept of the structure from conventional small-size display apparatus. In particular, a chassis of a conventional display apparatus is formed by bending a sheet metal. The reason why a chassis of the type is used is that, since it is small in size, a sufficient strength can be assured and an intended accuracy in dimension can be obtained even with a sheet metal and the cost is low.
However, if the chassis structure of a sheet metal is applied as it is to a display apparatus of a large screen, for example, of a screen of 40-inch or more size, then this gives rise to a disadvantage that a resulting chassis lacks in strength and is low in accuracy in dimension. Further, since metal dies are required for working of a sheet metal, metal dies of large sizes are required, resulting in an increase in cost. The present invention solves the problems described, and to this end, the present invention employs, as a material of the chassis, extruded members in the form of grooved steel bars or polygonal steel bars which are inexpensive, light in weight and high in strength. Such extruded members have not conventionally been applied to a chassis of a display apparatus.
Further, a conventional lighting apparatus adopts a structure wherein optical parts such as a light source like a fluorescent lamp, a light introduction plate, a reflecting plate or a diffusion plate, and other parts are accommodated in a casing in the form of a box made of a sheet metal, a synthetic resin or the like to integrate the components as a unit. If the structure is applied to a large size display apparatus of a 40-inch size or more by simply increasing the scale thereof, then the structure has a considerably high weight and this results in increase in weight of the display apparatus.
Therefore, as a first form of the present invention, a light source unit is formed from a light source and a reflecting plate, and an optical panel and a circuit board are attached independently of each other to a chassis. Since the chassis is formed as a rectangular frame having some depth, it serves also as a casing for a lighting apparatus. Accordingly, an independent box-shaped casing which forms the lighting apparatus is unnecessary, and consequently, significant reduction in weight of the set is achieved.
Further, a conventional display apparatus requires replacement of an entire lighting apparatus when a light source is deteriorated as a result of use thereof for a long time. Accordingly, where the display apparatus has a large screen, a high cost is required for such replacement. In contrast, with the display apparatus of the present invention, since only it is required to replace a necessary part, the cost for replacement can be decreased when compared with that of the conventional display apparatus. Further, in a display apparatus according to another form of the present invention, a side edge type light source unit composed of a light source, a reflecting plate, a light introduction plate and an optical panel is formed and incorporated in a chassis. Also with the display apparatus, a casing as a separate member for forming an independent lighting apparatus as in the prior art is not required. Accordingly, significant reduction in weight of the set can be achieved. Also replacement of the light source unit of the side edge type is facilitated.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.